T

Telemetry - The measurement of events at a distance. Transducers are used to measure physical activities and to convert these to signals that reflect the measurement of phenomena. The signals are transmitted, often over telephone lines, to a data collection center for processing. As a result of which, signals may be transmitted back to the distance location to control the process being monitored.

Three phase - Power supply incorporating three live conductors

Transceiver - A device used in data communication networks that can transmit and receive information

Transformer - A general term describing a component or device that magnetically transforms one alternating voltage to another without change of frequency. The usual construction is based upon two or more coils (or windings) of wire placed close to each other. The voltage change is proportional to the difference in the number of turns or windings between each coil.

Transient Control Level (TCL) - Term used in BS 6651:1992 to describe the portion of the transient overvoltage reaching equipment. This must be lower than the equipment transients design level or susceptibility level. In essence, transient control level means the same as let-through voltage.

Transient overvoltage - An increase in voltage between two or more conductors, lasting from microseconds to a few milliseconds in duration.

Transverse mode - See differential mode

Trunking - A square or rectangular surround, with removable cover, for mechanically protecting cables

Twisted pair - A cable consisting of a pair of conductors twisted around each other, in order to reduce interference. This is a simple and common communication medium widely used in telephony and other low-frequency applications.

U

UL - Abbreviation for the American Underwriters Laboratory, a testing and approvals body

Undervoltage - A decrease in the normal voltage level lasting for seconds or minutes. Also referred to as a brownout.

Uninterruptible power supply (UPS) - Contains batteries that store energy, which provides a power source during power interruptions.

Utility - A company that performs and essential utilitarian service, like providing natural gas and electricity for people.